Balanced jet nozzle and cooling means therefor



R. KRESS Nov. 5, 1957 BALANCED JET NOZZLE AND COOLING MEANS THEREFOR 2 Sheets-Sheet 1 Filed June 30, 1953 R. KRESS Nov. 5, 1957 BALANCED JET NOZZLE AND COOLING MEANS THEREFOR 2 Sheets-Sheet 2 Filed June 50, 1953 INVENTOR RALPH KRESS TTORNEYS United States Patent 0 Ralph Kress, La Mesa, Califi, assignor to Solar Aircraft Company, San Diego, Calif, a corporation of California Application June 30, 1953, Serial No. 365,005

9 Claims. (Cl. 6035.6)

The present invention relates to jet power plants and more particularly to nozzle structures for turbojet power plants and to means for varying the effective area of such nozzles.

As is Well known in the art it is essential that the flow of gases issuing from the nozzle of a turbojet engine be properly controlled to maintain the optimum relation between the volume and how rate of the gases under various operational conditions to maintain propulsive efficiency and avoid excessive back pressures within the engine. This is particularly true in connection with jet power plants equipped with afterburners which produce rapid variations in the temperature and volume of the gases discharged from the primary engine.

e initiation of afterburner combustion produces a rapid increase in the volume and temperature of the exhaust gases issuing from the nozzle, and conversely cessation of afterburning produces an immediate substantial reduction in the volume and temperature of exhaust gases. These rapid changes tend to disrupt the normal operating condition of the primary engine unless they are compensated for by correspondingly increasing and decreasing the effective size of the jet nozzle.

Compensation is also required for similar though smaller variations in the volume and temperature of the exhaust gases produced either during afterburning or non-afterburning operation by variations in the operational conditions of the aircraft including ambient temperatures, altitude and air speed.

Because of the critical importance of the variable area nozzle problem both in military and commercial aircraft, a number of attempts have been made in the past to improve nozzle performance. While many of these expedients are practical and useful they incorporate one or more relatively serious disadvantages which for the first time are eliminated or substantially minimized by the present invention.

Prior nozzle developments may be divided into three broad classes, the clam shell type disclosed and claimed in United States Patent 2,481,330; the multiple flap type illustrated in United States Letters Patent 2,603,062 and the bulb-type illustrated in United States Patent 2,557,431 issued to R. l. lmbert. A variation of the clam shell two-position nozzle is disclosed by United States Letters Patent 2,481,330. This nozzle comprises a pair of spaced arcuate members disposed on the longitudinal axis of the tailpipe of the jet power plant assembly and respectively hinged on axes transverse to the longitudinal axis. in this structure the arcuate members move toward and away from each other to vary the nozzle opening and are the sole moving elements and therefore require considerable movement to vary the size of nozzle exhaust between extreme operating conditions; which movements must be accomplished against the exhaust pressure of the axially discharging combusted gases. Such a system requires objectionably heavy and complex operating structures to move the arcuate members. Also it is difiicult to avoid fluid leakages around the various joints or parting sur- 2,811,827 Patented Nov. 5, 1957 faces defined by the arcuate members which cause turbulence and uneven exhaust flow. Further the aerodynamic drag and turbulence created by such nozzle control structures, especially when the nozzle structure is in the full open position has been found to be objectionable.

Further types of nozzle controls are those of the clam shell type disclosed in United States Patent No. 2,746,243 and a multiple flap type nozzle control of Patent No. 2,603,062.

While the foregoing have proved satisfactory in many installations they nevertheless may produce external aerodynamic drag by the creation of an area of stagnant air between the fuselage of the aircraft and the tailpipe when the clam shells or flaps are in the closed position. Additionally, considerable difiiculty has been experienced in sealing the slidable nozzle parts to minimize leakage. Also because of the relatively high operating forces needed to move the nozzle in direct opposition to the flow of exhaust gases such nozzles require relatively heavy actuating mechanisms and overly large fuselage structures to accommodate the control means.

A final type of nozzle is that disclosed by United States Letters Patent 2,557,435 issued to R. J. Imbert, and known as a bulb type nozzle. In this type of nozzle, a streamlined bulb is mounted within the exhaust duct or tailpipe and is longitudinally movable to selectively increase or decrease the area of the space between the inner periphery of the tailpipe and the outer periphery of the bulb to thereby control the amount of exhaust gases passing from the tailpipe. Although such constructions provide cleaner aerodynamic features they require complex actuating mechanisms working in the high temperature environs of the tailpipe and also require relatively powerful hydraulic actuators to move the bulb longitudinally inward of the tailpipe against the relatively high forces imposed on the bulb by the axially flowing exhaust gases. Since the bulb is the only movable element which adjusts the nozzle size, relatively large movements of the bulb are required to vary the nozzle for extreme conditions. Consequently the loads imposed by the exhaust gases effectively prevent rapid and efiicient adjustment when the bulb is being moved against the direction of such loads. In the past, nozzles of this type have been subject to rapid deterioration because of the failure to provide adequate means for supporting the nozzle for movement with the tailpipe and for cooling the nozzle bulb and nozzle supporting structures which are continuously directly exposed to the full exhaust gas temperature. For these reasons the bulb-type nozzle has not won acceptance despite its advantages.

In recognition of the deficiencies of these prior nozzles it is the primary object of the present invention to provide novel means for effectively and efficiently varying the discharge size of a nozzle continuously between full open and closed positions of a turbojet power plant with minimum force and range of movement of the nozzle. The structure of the present invention is particularly useful with jet engines equipped with afterburner structures, but is not restricted to use solely in such structures.

To accomplish this primary object the present invention comprises improvements in a bulb type nozzle of the general type disclosed by the Imbert patent. The structure comprises compound moving elements adapted for maximum adjustment with a minimum amount of movement and whose effective areas exposed to exhaust gas loads and directions of movement are such to nullify induced loads from the exhausting gases tending to resist adjustment of the nozzle. Additionally, as a result of the novel means for nullifying induced loads from the exhaust gases, Which thereby lessens the force required to effect adjustment, the utilization of materially less complex and lighter operating controls is possible thereby materially reducing the weight, complexity, and service problem heretofore encountered. The foregoing features when applied to the bulb type nozzle control of the present invention therefore result in a materially simpler, more efficiently operating, and aerodynamically cleaner structure than possible with prior art devices, heretofore known.

It is also, therefore, a primary object of this invention to provide novel exhaust means for a reaction type power plant which is of simple lightweight construction, is positive in operation and has an extended service life.

Another object of this invention is to provide an improved jet engine nozzle which alfords an exhaust opening fully variable between open and closed positions.

A further object of this invention is to provide a selectively variable nozzle for a jet engine having novel means of minimizing loads on the nozzle thereby requiring a minimum actuating force to effect adjustment of the nozzle for various operating conditions.

Still another object of this invention is to provide a selectively variable nozzle for jet engines having novel means which permit a relatively rapid movement of the nozzle to adjust the nozzle for changing operating conditions.

Yet another object of this invention is to provide a selectively variable nozzle for jet engines including a pair of members which move oppositely axially of the engine with respect to the movement of the exhaust gases.

, An additional object of this invention is to provide an improved selectively variable nozzle for jet engines including a pair of simultaneously oppositely moving members exposed to exhaust gas loads of the engine and interconnected'so that the exhaust gas loads on one member are eifectively balanced by the loads on the other member.

Still another object of this invention is to provide an improved selectively variable nozzle for jet engines comprising a movable bulb mounted in a tailpipe of a jet engine and a movable outer nozzle shell interconnected for simultaneous movement in opposite directions to effect rapid adjustment of the exhaust area of a jet engine with minimum effort.

Still a further object of thi invention is to provide an improved variable nozzle for jet engines having novel means for cooling the nozzle elements.

Another object of the invention is the provision of improved jet nozzle construction which eliminate the leakage of exhaust gases.

An additional object of this invention is to provide improved means for cooling the tailpipe structure of a jet engine. 7

These and other objects will become apparent from the following description and appended claims when read in conjunction with the attached drawing, wherein:

Figure l is a perspective view partially in section of a jet engine tailpipe showing the details of construction of the novel variable nozzle which constitutes this invention;

Figure 2 is a fragmentary sectional view taken subtantially along the line 22 of Figure 1;

Figure 3 is a fragmentary sectional view taken substantially along the line 3-3 of Figure 1;

Figure 4 is a fragmentary sectional view taken substantially along the line 44 of Figure 3;

- Figure 5 is a fragmentary sectional view taken substantially along the line 5-5 of Figure 1;

Figure 6 is a fragmentary sectional view taken substantially along the line fi6 of Figure 1;

Figures 7 and 8 are verticallyaligned diagrammatic views showing the relative position of the movable nozzle elements at their extreme settings. 7

Figure 9 is a partial vertical sectional view showing an afterstrut and a portion of the novel cooling means of this invention; and

Figure 10 is a partial vertical sectional view showing another portion of the novel cooling means of this invention.

Referring now to the drawing and more particularly to Figure l the numeral 20 generally indicates a tailpipe for a jet engine comprising a diffuser section 22, an afterburner section 24, a nozzle section 26, and an adjustable nozzle 27. Afterburner section 24 is removably connected to the rearward or aft end of diffuser 20, and nozzle section 26 is removably connected to the aft end of the afterburner to define the substantially unitary tailpipe structure 20 which is removably secured at the forward end of diffuser 22 through flange 28 and suitable means (not shown) such as bolts to the after end of a primary engine (not shown). Within tailpipe 20 and at its forward end adjacent flange 23 is a tail cone 30 which defines an annulus within the diffuser section for the controlled flow of gases from the turbine within the primary engine. in jet engines equipped with afterburner structures, such as illustrated, additional fuel supply means such as fuel pipes 31 deliver fuel to a distributor ring 32 to which pipes 33 are connected for receiving and delivering combustible fuel to a plurality of circumferentially disposed spray nozzles 34 mounted adjacent flame holder 36 in the afterburner structure.

As is Well known in the art of jet engines, air enters at the forward end of the power plant and is compressed by a compressor therein. Fuel is supplied to the compressed air, the resulting mixture is burned and the exhaust gases pass through a turbine which drives the compressor and thereafter issue from the nozzle as a propulsive jet. it has been found in practice that approximately 25% of the air passing through the primary engine system is combusted, the remainder being necessary for cooling parts of the primary engine. Additionally, fuel is admitted through spray nozzles 34 to be combusted with the excess air aft of the primary engine which greatly augments the thrust gained from combustion in the primary engine and increases the operating efliciency of the aircraft. Flame holder 36 is so positioned in the burner section to assure ignition and a stable flame pattern, as is well known in the art. V In the case of an afterburner equipped power plant, afterburner combustion increases the volume and temperature of the gases discharged, therefore, to prevent restrictive buildups in back pressure and loss of efiiciency the nozzle should be relatively wide open and is so adjusted, while conversely with the afterburner inactive or not functioning and a consequent lower volume of combusted gas a rapid discharge of the gases results in a loss of thrust efliciency, therefore, the nozzle is set at a constricted position to prevent rapid discharge of the gases. Whetherthe power plant is equipped with an afterburner or not the area of the nozzle for optimum thrust efficiency must be varied to be in constant ratio to the pressures created by the combustion of the fuel. The more rapid and easy the adjustment of the nozzle is, the more efficient is the operation of the aircraft regardless of the rapidity of change of the operational condition. The novel adjustable nozzle of the present invention permits such adjustment and will now be presently described.

Inner tail cone 3i) within diffuser 22 is maintained therein in spaced relation to the walls of the diffuser by a plurality of equally disposed aerodynamically faired hollow struts 38 preferably three in number spaced degrees apart, more fully described in application Serial No. 157,747, filed April 24, 1950 and now abandoned. The downstream end of tailcone 30 is extended axially substantially coextensive with the tailpipe in the form of hollow tubular member 49. Near the aft end of tailpipe 20 tubular member 40 is supported in spaced relation to the walls of the tailpipe by. hollow aerodynamically faired struts .42, preferably three in number disposed approximately 120 degrees apart.

Slidably mounted on the outer periphery of and at the extreme downstream end of tube 40 is a bulb assembly generally indicated 46 which comprises a streamlined outer shell 48 having a substantially cylindrical portion 50, an enlarged portion 52, and a reduced orifice portion 54. An inner shell 56 is mounted within the enlarged and reduced orifice portions of the outer shell and conforms in shape to these portions and is provided with a plurality of outwardly extending peripheral dimples 58 which contact the inner wall of the outer shell and support the inner shell therein in spaced relation to the outer shell. Suitable means such as spot welds or blind rivets rigidly secure the inner shell and outer shell at the contact points of the dimples.

As clearly seen in Figure 6, both inner and outer shells 56 and 48 respectively can be constructed in half sections and then joined by suitable means such as spot Welding or riveting. This construction permits one end of each half section of inner shell 56 to be constructed slightly longer than the other end of the section to permit forming, as by bending, into diametrically opposed radially inwardly extending ribs 57 which are bent at their inner ends to form right angle flanges 59 rigidly secured to the periphery of an elongated hollow tube. The ribs 57 are cut away as at 63 to permit movement of the bulb 46 with respect to the tube 40.

Secured by suitable means such as welding or brazing to the inner wall of the outer shell at the juncture of portions 59 and 52 are a pair of concentric bands indicated at 60 which are bent inwardly to form a spaced groove for mounting woven sealing element 62 in sliding sealing contact with the periphery of tube 40.

Tube 64 is mounted in sealing relation and rigidly secured at one end, as by welding to the orifice portion of inner shell 56 as indicated at 66, and also to flanges 59 as heretofore described. The opposite end of tube 64 is slidably supported within tube 40, as will be presently described.

Cylindrical sheet heads 68 are rigidly secured in axially spaced sealing relation within tube 40, as by welding, and are provided with axially aligned central apertures 78, as clearly seen in Figure 3. At three points approximately 120 degrees apart each bulk head is provided with a cut away portion or slot 72 extending radially outwardly from aperture 70'. Slot 72 is formed by slitting the metal along what is to be the center of the slot and then cutting away portion '74. The metal on either side of the slit is then bent at right angles to the bulk head to form spaced ears or legs 76 for purposes of mounting rollers 78. Headed roller axles 80 are mounted in suitable aligned apertures in each pair of legs 76 and are secured therein by cotter pins 82. Bearing washers 84 are disposed on the outermost sides of each leg 76 to prevent excessive wear. Rollers 78 are mounted on bearings 86 which are in turn rotatably mounted on roller axles Rollers '73 are provided with a concave periphery as indicated at 88 to engage the periphery of tube 64 to guide the tube, for longitudinal movement as will be hereinafter described.

In order to prevent fluid leakage through slots 72 a seal mounting assembly generally indicated at 90 is secured to forward or upstream bulkhead 68, as best seen in Figure 4. The seal mounting assembly comprises a flange portion 92 seaiingly secured to the rear face of bulk head 68, as by welding, and having a shoulder portion 94 which extends transversely from the bulk head a sufilcient distance to provide clearance between rollers 78 and inwardly extending flange or disc portion 96. Secured in leak proof relation to the rear face of disc portion 96 is a member 98 which defines, with disc portion 96, a groove 160 for mounting heat resistant woven metal annular packing 102 in sealing engagement with the periphery of slidable tube 64. For purposes of strength seal 102 is backed by a circumferential band 104, as clearly seen in Figure 4.

Mounted within and in spaced relation to tube 40 and disposed between and fixedly secured at its upstream or forward end, as by welding to upstream bulk heads 68 is sleeve member 106 which defines with tube 40 an annular channel 108 for the passage of cooling air, as will hereinafter be described. The downstream end of sleeve 106 is slightly spaced from downstream bulk head 68 and has an inwardly bent portion 109, as clearly seen in Figure 1. The rearmost or right hand bulk head 68 as viewed in Figure l is provided with a plurality of apertures 110 opening into annulus 10S adjacent portion 169 to allow passage of cooling air therethrough, as will become apparent.

Also mounted within hollow tube 40' and defining with the tube annular space 112 is sleeve 114 having flange 116 at one end sealingly connected to the inner wall of tube 40. The opposite end of sleeve 114 is spaced a slight axial distance from forward bulk head 68 and is provided with integral inwardly directed flange 118, for a purpose to appear. Suitable support means (not shown) also serve to support sleeve 114 in tube 40 intermediate its ends. A plurality of apertures 120 adjacent the downstream face of flange 116 are suitably connected to air ducts or pipes 122 connected to the compressor outlet, for a purpose to be described.

Referring now to Figure 5 in conjunction with Figure l, aft struts 42 comprise an outer aerodynamically faired shell 124 having flanges 126 at opposite ends rigidly secured to the periphery of tube 4% and inner wall of nozzle section 26 as by spot welding. Inner airfoil shaped shell 128, closed at both ends by plates (not shown), for a reason which will become apparent, mounted in spaced relation to outer shell 124, to define an annular space 131), is held in spaced relation with shell 124 as by brackets 132 spot welded to the respective shells. Tube 40 is provided with a plurality of apertures 134 connecting the inside of tube 40 with annular space 130.

Mounted on and encircling the outer periphery of nozzle section 26 overlying the juncture point of struts 42 and nozzle section 26 is a channel member 136 secured in leak proof relation to the nozzle section, as by welding, which defines a peripheral space 138 therebetween. Suitable apertures 137 in nozzle section 26 connect space 138 with annular space 136 of struts 42. A plurality of axially extending channels 149 are mounted in leak proof relation on the nozzle section and are interconnected with space 138 of channel member 136. Fittings 142 are suitably mounted at the upstream end of axial channels and are adapted for connection to ducts or tubes (not shown) suitably connected to the compressor discharge for directing cooling air into struts 42 and bulb assembly 46, as will be hereinafter explained.

Also mounted on nozzle section 26 is a bracket 144 having a circumferentially outwardly open groove for mounting an annular heat resistant woven metallic packing 146 therein. As best seen in Figure 1 the extreme donwstrearn end of nozzle 26 is flared to form outwardly directed arc rim 148, common in standard orifice forms.

Adjustable nozzle section 27 is slidably supported on packing 146. The nozzle section is formed of a pair of annular sheet metal members 150 and 152 respectively connected together in leak proof relation as by welding. Section 150 is substantially cylindrical, as clearly seen in Figure 1, while section 152 is of generally parabolic crosssection with the outermost inwardly directed curved portion 156 defining the outlet portion of the nozzle.

In the present invention adjustable nozzle assembly 27 and adjustable bulb assembly 46 are constructed for simultaneous movement in opposite directions, and the control means for imparting movements to these assemblies will now be described.

Referring to Figure 2 in conjunction with Figure 1 an actuating rod 158 is pivotally mounted in each of the struts 38 extending interiorly to a point adjacent the longitudinal axis of the diffuser 22 and exteriorly of the dilfuser .through suitable slots 159. As clearly seen in Figure 1, the point of pivoted support of rods 158 is closer to the outer end of rod-158 than the inner end, for a purpose to be described. As clearlyseen in Figure 2, each strut is provided with spaced axially aligned apertures 160 and spaced journals 162 mounted in surrounding relation to each aperture and welded to the walls of strut 38. To reduce weight, rods are con- 7 structed of a pair of spaced sheet members 164 connected at opposite ends by welding and having axially aligned bores in which a hollow sleeve 166 is mounted and rigidly secured thereto, as by weld 168. A bearing 17% is inserted into hollow sleeve 166 and the rod is then inserted into strut 38 with the bore of bearing 170 in axial alignment with the bore in the strut and the journal bores. Axle or pivot member 172 is then passed through one of the bores of the strut to rest in the bores of spaced journals 162 and is rigidly secured therein as by cotter pin 174- passing through suitably aligned apertures in a journal and the pivot member, as clearly seen in Figure 2.

Opposite ends of rod 158 are provided with apertures for receiving pivot pins for pivotally mounting the bifurcated arms of thread adjustment connectors 176 and 178. Connectors 176 adjustably engage rigid connecting rod 180 at one end, as by means of threads, the opposite end of rod being suitably connected to respective brackets 182 rigidly mounted and disposed substantially 120 apart on the outer periphery of section 150 of nozzle 27. Connectors 178 at the inner end of rod 158 similarly engage one end of rigid rods 184 which pass through the center of tube 40 and are suitably connected to brackets 186 rigidly mounted and disposed substantially 120 apart on the periphery of tubular member 64, as by Welding.

Operation and method of adjustment of discharge orifice Turning now to Figures 7 and 8 in conjunction with Figure 1, the operation of the novel balanced bulb nozzle will now be described. I

For purposes of comparison the figures are illustrated in the same relative position; that is, the left hand end of the diffusers 22 of Figures 7 and 8 are located on the same vertical line thus a comparison of the relative movements of the adjustable nozzle and bulb is possible. The operation will be described in connection with a jet engine equipped with after-burner structure, however, as heretofore noted, the invention and operation is equally applicable to the primary engine alone.

The adjustable nozzle 27 and movable bulb 46 can be moved longitudinally and positioned at various positions intermediate the minimum nozzle opening indicated by A in Figure 7 and the maximum nozzle opening indicated by B in Figure 8.

As heretofore noted, when the afterburner is being used the nozzle is preferably wide open as at B to permit proper exhaust without a restrictive build up of back pressure, while conversely under low power conditions it is desirable to restrict the nozzle opening as at A to prevent too rapid an exhaust and consequent loss of thrust efliciency. When afterburning is initiated, lever 158 is rotated clockwise about pivot member 172 by suitable Figures 7 and 8. This movement of both nozzle 27 and bulb assembly 46 will move portion 52 of the bulb away from the type constricted end 156 of nozzle 27 to increase the nozzle opening from the minimum condition indicated by A to any opening up to the maximum indicated by B. When afterburning is discontinued and it is desired to constrict the efiaust, lever. 158 rotated.

counterclockwise which imparts the opposite forces to rods 180 and 184 to pull nozzle 27 upstream or to the left and simultaneously move bulb assembly as downstream or tothe right.

From the earlier detailed description it Will be readily seen that sliding movement of nozzle assembly is permitted by the slidable support of nozzle s ection 150 on packing 146. Sliding movement of bulb assembly 46 is permitted by the sliding support of tube 64 on rollers 73 and the sliding engagement of seal 62 with tube 40.

Again referring to Figures 7 and 8, in prior art adjustable bulb type nozzles where only the bulb is movable to adjust the discharge annulus powerful mechanism is necessary to move the bulb upstream against the loads imposed on the forward projected area of the bulb by the axially downstream flowing exhaust gases. It has een found in practice that the force required to move the bulb might under certain conditions be as high as 6000 pounds. Obviously, the mechanism necessary to develop this degree of moving pressure is objectionably complex and heavy.

The movement of the bulb and nozzle in opposite directions coupled with the proper selection of pivot member 172 between the extremities of lever 158 serve to balance the loads imposed on the projected areas of the nozzle and bulb indicated at D and C, respectively, even though these areas are not the same. That is, considering movement from the condition of Figure 7 to Figure 8 the load imposed on projected area D is aiding movement of nozzle 27 downstream while the load imposed on projected area C is opposing movement of bulb upstream. Fulcrum point 172 is so located that the load on area D multiplied by lever arm X is substantially equal to the load imposed on area C multiplied by lever arm Y, so that the imposed loads on the nozzle and bulb effectively offset each other or are in substantial equilibrium. Under these conditions it has been found in practice that a'force of'less than 300 pounds from the actuator (not shown) 'is all that is necessary to overcome frictional drag and other minor causes of resistance to effect rapid movement in either direction.

Also with both a movable nozzle and bulb the effective adjustment is far more rapid than heretofore possible since in prior art devices where only the bulb was movable the'bulb had to move through a distance equal to the sum of distances E and F indicated in Figures 7 and 8. With the present novel relation of oppositely moving nozzle and bulb the nozzle need only move the distance E while'the bulb need only move the distance F to effect an adjustment of the discharge annulus from the extreme closed position to the extreme open position indicated by A and B respectively.

The novel arrangement of both an adjustable shell and r bulb assembly also permitsthese members to be interconnected in such a manner as to permit automatic selfadjustment to the most suitable orifice opening size should the actuating mechanism fail or otherwise become damaged.

As heretofore described pivot pins 172 can be located between the ends of levers 158 so that the load on projected area C multiplied by its lever arm Y can be balanced by the load on area D multiplied by its lever arm X, and the only forces necessary to adjust the nozzle are those necessary to overcome the friction of the system. However, pivot pins 172 can also be located to have an unbalance between the loads on the respective areas so that therewill be an inherent tendency of the shell and bulb assemblies to automatically move to a particular setting,- where there is no restraint exerted by the actuating 0r 7 control mechanism restraining such movement.

For example, if in the particular aircraft installation afterburning can be instantaneously cut off, then in the event of control failure or damage of theactuating mechanism it would be desirable to have the orifice in its closed condition, illustrated by Figure 7,to prevent lossof thrust by an overly rapid exhaust. By virtue of the novel dual adjustment members of the present invention this is easily accomplished by a relocation of pivots 172 so that the load on area C multiplied by lever arm Y is greater than the load on area D multiplied by arm X. With these conditions should the actuating mechanism fail bulb assembly 46 would move downstream or to the left as vieved in Figure 7, pulling shell assembly 27 upstream to define the closed orifice position of Figure 7.

Conversely, should the particular installation be such that afterburning cannot be immediately cut off then it would be more desirable to have the orifice in the open position to prevent excessive build ups in temperature and back pressures in the tailpipe. In this case pivots 172 and so positioned that the load on area D multiplied by lever arm X is greater than the load on area C multiplied by lever arrn Y so that the result, in the case of control failure, is the downstream movement of shell assembly 27 and consequent upstream movement of bulb assembly 46 to the open orifice position of Figure 8.

Thus it can be readily seen that with the novel interrelated movable shell and bulb assembly of this invention provision can be made so that these members will automatically adjust themselves to the most suitable orifice opening, in the event of control failure or damage, to permit continued safe operation of the aircraft.

Thus it is readily seen that more positive rapid adjustment of the discharge annulus is possible with a minimum of actuator pressure than heretofore possible with any prior devices, known to me.

Operation of cooling means As previously described, tube 122 and fitting 142 are connected to the compressor discharge area (not shown) in order to direct cooling air from the compressor to the bulb assembly 46, struts 42 and other components located in the hot atmosphere of tailpipe 20. Because any cooling air directed to the tailpipe is rapidly heated, two separate and distinct cooling paths for cooling air through the tailpipe are provided to effectively cool all areas efficiently.

Referring now to Figures 1, 7 and 8 cooling air from the compressor passes through tube 122 through aperture 120 into annulus 112 and flows longitudinally downstream in the annulus to the end of sleeve 114. Since forward bulk head 63 is provided with seal 102 preventing passage of air thereby, the air flows radially inwardly around rim 118 and then backward or upstream a slight distance to the end of tube 64 where it then enters tube 64 and flows axially downstream to be discharged at the end of tube 64 to the ambient air. This passage of air effectively serves to cool tube 40, sleeve 114, and tube 64 which slides on seals 102. The cooling of tube 64 effectively reduces the deleterious effect of heat on seals 102 and effectively lengthens their service life. In order that cooling air flowing over rim 118 passes into tube 64 and does not flow upstream in the larger diameter tube 40, a bulk head 192 is fixedly sealingly mounted, as by welding, in tube 40 sufficiently upstream so as not to interfere with axial movement of tube 64, as clearly seen in Figure 10. Bulk head 192 is provided with suitable apertures 194 to permit actuating rods 184 to extend therethrough, and if desired low friction heat resistant grommets can be mounted in the apertures to prevent the escape of air upstream in tube 40. Thus when cooling air passes into tube 40 from annular passage 112 it is effectively prevented from passing upstream through large diameter tube by bulk head 192 and therefore must pass through smaller diameter tube 64 downstream to the ambient air.

Additional cooling air is fed from the compressor discharge to fitting 142 through a suitable tube (not shown) and passes axially along channel 140 into ring channel 136 from whence it passes through suitable apertures into passages or spaces 130 of struts 42 which are 10 relatively restricted to impart relatively high velocity to the air. The air then passes through apertures 134 into annulus 108, which serves to maintain the air velocity, and discharges from annulus 108 by means of apertures 110 in aft bulk head 68. Since inner shell or bulb 56 is secured in sealing relation to tube 64 air cannot pass directly to the atmosphere but will circulate within the interior of the bulb and curl or flow upstream over the upstream end 188 of inner bulb 56 and then into the space between inner and outer bulbs 56 and 48, respectively, defined by dimples 58 and from this space the air will discharge at reduced end of the outer bulb. It is clearly seen that the last described passage of air serves to effectively cool struts 42, the after end of tube 40,

seal 62, seals 102 and bulb assembly 46. Thus the two distinct paths of air assure the delivery of sufficient relatively cool air to separate zones of the tailpipe to assure maximum efiicient cooling of the various elements functioning in the environs of the hot exhaust gases From the foregoing it will be readily seen that the present invention provides novel means for effecting rapid and eificient adjustment of the discharge annulus of a jet power plant to attain maximum thrust efliciency at all operating conditions with a minimum of effort and with relatively simple lightweight mechanisms. Additionally, the present invention provides improved means for cooling the various elements, which of necessity must function in the environs of the hot exhaust gases of a jet engine to eifectively diminish the deleterious effects of the gases on these various elements.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a jet engine having an elongate tailpipe; an open end in said tailpipe for permitting combusted gases to flow axially of said tailpipe and exhaust to the atmosphere; a pair of coaxial members mounted for opposite movement with respect to said tailpipe defining a variable area exhaust orifice and each having an area exposed to the axially flowing combusted gases; and an actuating mechanism for imparting simultaneous opposite movements to said members so related to the areas of said members that the axial gas loads on one member are substantially nullified by the axial gas loads on the other member whereby said members can be rapidly selectively moved with a minimum of effort to vary the area of said orifice for various operating conditions.

2. In a jet engine having an elongate tailpipe; an open end in said tailpipe for permitting combusted gases to flow axially of said tailpipe and exhaust to the atmosphere; a substantially frusto-conical member movably coaxially mounted on said tailpipe at said open end and having an inner area exposed to said axially flowing gases; a bulbous member movably mounted in said tailpipe at said open end defining with said frusto-conical member a variable area exhaust orifice and having an area exposed to the axially fiowing gases; and actuating means operatively connected to said member for imparting simultaneous opposite movements to said members and so related to the projected areas of said members that the axial loads imposed by said gases on one of said projected areas is substantially nullified by the gas loads on the other of said projected areas whereby said members can be rapidly selectively moved with a minimum effort to vary the area of said orifice for various operating conditions of said jet engine.

3. The device as set forth in claim 2 wherein said actuating means comprises lever means operatively connected to said members and fulcrumed in said tailpipe so that the loads on said areas are effectively balanced.

4. In a jet engine having an elongate tailpipe, an open end in said tailpipe for permitting combusted gases to flow axially of said tailpipe and exhaust to the atmosphere; a substantially frusto-conical member movably coaxially mounted on said tailpipe at said open end and having an inner area exposed to said axially flowing gases; a bulbous member movably mounted in said tailpipe at said open end defining with said -frusto-conical member a variable area exhaust orifice and having an area exposed to the axially flowing gases; means defining a plurality of separate passages through said bulbous member; means for separately delivering cooling air to said passages to efiiciently and completely cool said bulbous member; and actuating means operatively connected to said members for imparting simultaneous opposite movements to said members and so related to the areas of said members that the axial loads imposed by said gases on one of said areas is substantially nullified by the gas loads imposed on the other of said areas whereby said members can be rapidly selectively moved with a minimum effort to vary the area of said orifice for various operating conditions of said jet engine.

, 5. The device as set forth in claim 4 wherein said bulbous member comprises a pair of shells mounted in spaced relation defining a passage therebetween for said cooling air and wherein an axially extending tubular member defines another passage for cooling air.

6. in a jet engine having a tailpipe for axially flowing exhaust gases; an open end in said tailpipe for permitting said axially flowing gases to exhaust to the atmosphere; a first member coaxially movably mounted on said tailpipe adjacent said open end defining an outer nozzle member; a second member coaxially movably mounted in said tailpipe at said open end defining an inner nozzle member and cooperating with said outer nozzle member to define a variable area exhaust orifice, said members each having inclined surfaces exposed to said gases; a lever pivotally mounted in said tailpipe; and means connecting said inner and outer nozzle members to respective arms or" said lever whereby movement of said lever simultaneously imparts opposite movementsto said inner and outer nozzle members to vary the area of said ex haust orifice, the length of said lever arms being in predetermined relation with the projected areas of said surfaces to reduce the force required to move said members.

7. in a jet engine, an elongate tailpipe defining an axial path for combusted gases; an open end in said tailpipe to permit said gases to exhaust to the atmosphere; a hollow support member coaxia'lly mounted in 'said' tailpipe; axially spaced mounting members mounting said support member in said tailpipe; a selectively movable nozzle assembly mounted in said tailpipe adjacent said open end; control means extending through said support member and operatively connected to said nozzle assembly for imparting selective movements to said nozzle assembly to vary'the fiow of said gases; means defining a cooling air passage through one of said mounting members, support, and nozzle assembly; means defining a separate cooling air passage through another of said memhers, support, and nozzle assembly; and means for separately delivering air to each of'said cooling air passages, whereby all portions of said mounting members, support,

nozzle assembly are cooled.

8. in a jet engine having a tailpipe through which combustion products flow; a nozzle bulb assembly for con-' trolling the flow of said combustion products, said bulb being of double walled shell construction; a central hollow member in said bulb; support means in said tail pipe for supporting said hollow member for movement along the axis of said tailpipe; a plurality of axially spaced strut assemblies for mounting said support means in said tail pipe at spaced points along its length; means forming a first cooling air passage through one of said strut assemblies, said support means and said hollow member; means forming a'separate cooling air passage through the other of said strut assemblies, a portion of said support means, and said double wall of said bulb; and means for delivering cooling air to each of said passages.

9. The combination according to claim 8 wherein said double wallednozzle bulb assembly comprises an outer shell of bulbous form; a reinforcing liner of substantially I the same configuration as said outer shell, said liner having a plurality of integral projections for attachment to said shell; and a plurality of radial spokes connecting said liner to said central hollow member.

References Cited in the file of this patent UNITED STATES PATENTS 2,483,401 Cole Oct. 4, 1949 2,510,506 Lindhagen et al. June 6, 1950 2,540,594 Price Feb. 6, 1951 2,570,629 Anxionnaz'et al. Oct. 9, '1951 2,573,982 Ofeldt Nov. 6, 1951 2,575,735 Servanty Nov. 20, 1951' 2,630,673 Woll Mar. 10, 1953 2,641,104 Estabrook June 9, 1953 

